The immunology of the hygiene hypothesis of allergy is complex and involves the loss of cellular and humoral immunoregulatory pathways as a result of the adoption of a Western lifestyle and the disappearance of chronic infectious diseases. The influence of diet and reduced microbiome diversity now forms the foundation of scientific thinking on how the allergy epidemic occurred, although clear mechanistic insights into the process in humans are still lacking. Here we propose that barrier epithelial cells are heavily influenced by environmental factors and by microbiome-derived danger signals and metabolites, and thus act as important rheostats for immunoregulation, particularly during early postnatal development. Preventive strategies based on this new knowledge could exploit the diversity of the microbial world and the way humans react to it, and possibly restore old symbiotic relationships that have been lost in recent times, without causing disease or requiring a return to an unhygienic life style.
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Allergy, Asthma & Clinical Immunology Open Access 27 November 2023
What inhalant allergens can do and not do?—The cooperation of allergens and their source in Th2 polarization and allergic sensitization
Allergo Journal International Open Access 28 July 2023
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B.N.L. and H.H. are supported by Ghent University (Concerted Research Initiative (GOA) grant) and by the Scientific Research Foundation Flanders (FWO).
The authors declare no competing financial interests.
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Lambrecht, B., Hammad, H. The immunology of the allergy epidemic and the hygiene hypothesis. Nat Immunol 18, 1076–1083 (2017). https://doi.org/10.1038/ni.3829
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